DE 41 11 734 C1 discloses a method in which a plurality of inverters are connected in parallel in order to feed current from at least one DC source into an AC grid. In this case, the inverters have one output for each phase of the AC grid, wherein the outputs of different inverters which belong to one phase of the alternating current are connected to a phase connection for the corresponding phase of the alternating current via decoupling inductors. In order to minimize a transverse current which may occur between the inverters if said inverters have a different switching response, a potential control command to one of two inverter strings between which a transverse current occurs is temporarily reversed. For this purpose, the currents flowing from the two inverter strings are compared using a comparator, by means of which the reversal of the potential control command is triggered when a limit value is exceeded. This reversal is only canceled again when the transverse current has fallen below the limit value again.
It is conventional to provide a line filter inductor between a common phase connection, to which a plurality of inverters are connected via decoupling inductors, and the associated phase of an AC grid.
US 2010/0165678 A1 discloses an arrangement for converting a direct current into a polyphase alternating current, wherein the arrangement has a plurality of inverters. Each of the inverters has one output for each of the phases of the alternating current, wherein the outputs of the inverters which are assigned to the same phases are each connected to a phase connection. In order to suppress transverse currents between the inverters, a first inductor comprising an inductor winding on a magnetic core is provided between each output and an intermediate point. A second inductor comprising an inductor winding on the same magnetic core as an inductor winding of a first inductor of another inverter assigned to the same phase is provided between this intermediate point and the associated phase connection. The cores on which the inductor windings of the first inductors, assigned to the different phases, of each inverter are arranged are magnetically coupled to one another, i.e. parallel limbs of an EE core.
DE 10 2007 063 434 A1 discloses an inverter system comprising a plurality of inverters electrically connected in parallel, i.e. the inverters having one output for each phase of an alternating current output to a load. An inductive coupling unit is provided for these outputs, in which the currents of one phase of all of the inverters are coupled by an inductor. I.e., the inductors of the inverters assigned to the same phase are arranged on a common magnetic core. The coupling unit acts as a differential mode inductor and thus only damps circulating currents. Specifically, the inductors which are assigned to the outputs of the inverters for the same phase are arranged on parallel limbs of in each case one core.
EP 2 237 404 A1 discloses an inverter apparatus comprising two full-bridge circuits connected in parallel. A filter inductor for the output alternating current is arranged in the two output lines of each full-bridge circuit. In this case, the filter inductors are magnetically coupled to form a double inductor in those two lines of the two full-bridge circuits which lead to the same output of the apparatus. The double inductor comprises two windings on a common core, wherein one winding end is connected to an AC output of the apparatus directly or via further filter elements, while the other winding end is connected to one of the outputs of the two full-bridge circuits.
DE 293 758 A discloses a device for compensating for no-load current in the case of coils with an iron core. In this case, a plurality of metal strips which are insulated from one another are laid around a coil core such that in total they represent a coil with a high inherent capacitance. The metal strips are wound around the coil core in addition to a primary and secondary winding. The inner end of each metal strip is connected to the outer end of the adjacent metal strip by a Z-shaped conductor, with the result that the metal strips are connected in series. The outer end of the first metal strip and the inner end of the last metal strip, however, remain open.
There still is a need of an inductor device which is optimized in terms of its manufacturing complexity and an apparatus having such an inductor device which is thus optimized, and by means of which electric current can be fed from at least one DC source into an AC grid via a plurality of inverters.